Argentine fossils shed light on vicious group of dinosaurs

WASHINGTON (Reuters) - Fossils of a carnivorous dinosaur unearthed in Argentina are shedding new light on an intriguing group of predators that apparently were just as happy to slash victims to death with sickle-shaped hand claws as to chomp them into an early grave.

Scientists said on Wednesday the creature, called Murusraptor barrosaensis, lived about 80 million years ago during the Cretaceous Period, measured about 21 feet (6.5 meters) long and was a pursuit hunter more lightly built than some other predatory dinosaurs.

Murusraptor was a member of a group of meat-eaters called megaraptors, meaning "giant thieves," that prowled Patagonia, although fossils of relatives have been discovered in Australia and Japan.

"Most of the different species known from this clade are based on rather fragmentary specimens. The Murusraptor specimen preserved the complete posterior half of the skull, several vertebrae and pelvis bones, unveiling unknown areas of the skeleton of this group," said paleontologist Rodolfo Coria of Argentina's Universidad Nacional de Río Negro.

"The braincase is complete, and is the only known among megaraptors," Coria added. "It brings a unique opportunity to search for characteristics of neurological development in these dinosaurs."

Megaraptors were medium-sized predators compared to some of Argentina's giant Cretaceous meat-eaters, like the roughly 41-foot-long (12.5 meters) Giganotosaurus, and likely hunted in a different way. Giganotosaurus, which lived about 17 million years before Murusraptor, had a massively built skull and large teeth for killing prey, along with puny arms that would have done little good in hunting.

Other scientists last week announced the discovery of fossils of another Argentine carnivorous dinosaur, called Gualicho, a bit larger than Murusraptor that had feeble arms, akin in size to a human child's.

In contrast, megaraptors possessed strong arms that wielded sickle-like claws that could inflict fatal wounds on prey, along with a more lightly built skull and jaws studded with smaller teeth. They also had air-filled, bird-like bones.

But that certainly did not mean an encounter with Murusraptor in prehistoric Patagonia would end well.

"A person might say, ​'Oh my god, a megaraptor!' And then he would die," Coria added.

​Murusraptor means "thief from the wall," because its fossils were collected from the wall of a creek in Argentina's Neuquen Province.